code: def get_data(t1, t2):
      df1 = getattr(SERVER_CONTEXT, t1)
      df2 = getattr(SERVER_CONTEXT, t2)
      data = df1.join(df2, lsuffix=f"_{t1}", rsuffix=f"_{t2}").dropna()
      data["t1"] = data[f"Close_{t1}"]
      data["t2"] = data[f"Close_{t2}"]
      data["t1_returns"] = data[f"Returns_{t1}"]
      data["t2_returns"] = data[f"Returns_{t2}"]
      return data
  
file_path: bokeh/examples/server/app/stocks/main.py
imports: from functools import lru_cache
  from bokeh.layouts import column, row
  from bokeh.models import ColumnDataSource, PreText, Select
  from bokeh.plotting import curdoc, figure
label_desc: Use image node_id 2 for calling a global function with example usage: get_data(t1, t2) and returns: data